signal splitting and calculations

[AM]

I'm running my guitar cable through a buffered Boss pedal and then to the amp. Pedal's output impedance is 1 Kohm.
If I'll use a Y adaptor at the output jack and run from there two cables to two amps what do I change to the impedance? In numbers I mean.

[ashcat_lt]

The amp inputs will be in parallel, so you figure the load impedance just like any parallel resistance. 

Your pedal will drive several amplifiers in parallel without any noticeable losses.

[R.G.]

I'm running my guitar cable through a buffered Boss pedal and then to the amp. Pedal's output impedance is 1 Kohm.
If I'll use a Y adaptor at the output jack and run from there two cables to two amps what do I change to the impedance? In numbers I mean.

The short answer is - you don't.

Impedance matching sounds gee-whiz, but it's only used when there is some issue with needing as much power transferred as possible. This is most particularly NOT the case when you're driving guitar amps.

Guitar amps nearly all have high impedance inputs, usually 1M or more. A 1K output impedance from a Boss pedal will drive one, two, or up to about 1000 or more (no, not a typo, one thousand or more) without significant problems from the pedal impedance or amp impedance.

You **want** low impedance things driving higher impedance things in a world of transferring voltage (like we want in audio-land) instead of power (like the outputs of tube amps to speakers).

[PRR]

> If I'll use a Y adaptor at the output jack and run from there two cables to two amps what do I change to the impedance?

Different way of looking at it:

The output of the power-line from the street to my house is about 1 Ohm.

A 15 Watt lamp is about 1000 Ohms.

I can plug-in one lamp. Fine.

I can get a power-strip and plug in 2 lamps. Fine. Or 3 lamps. Fine.

I can hardly measure the difference. "120V" sags to 119.6V. My meter-eye is not that sharp. I sure can't tell the difference by the light the lamps give.

Even several dozen lamps makes less difference than power-company tolerance.

If I plug in *1,000* lamps, now I have a 1000/1000= 1 Ohm total load, against the 1 ohm of my power-line. That's very saggy. "120V" becomes 60V and the lamps run dim.

Situations like this, it is "normal" to be able to feed dozens, even hundreds, of minor loads withOUT any concern. You don't go around your house counting lamps before you plug-in another one. (Maybe this week with 50,000 Xmas lights.)

One gotcha. With simple plug-splitters, if one load is shorted all loads lose their feed. If I axe the light on the stairs, the whole basement goes dark. If your spike-heel boot pinches the cord to either amp, both amps go silent. When I used to feed dozens of idiots with concert-recorders, that was an issue, and there's ways to isolate. But for one user and just two destinations, you'll be careful.